What are the use levels for titanium dioxide or zinc oxide in sun care formulations?
Inorganic sunscreens are used over a wide range on concentration, from less than 1% to more than 20% solids. In the USA, the latest version of the Sunscreen Monograph requires that each UV filter in a formulation must contribute at least two SPF units to the overall SPF of the formulation. At typical efficacy levels, the minimum concentrations to meet these requirements would be about 1% titanium dioxide, or about 2% zinc oxide. In most countries, there is a maximum level of 25% for titanium dioxide or zinc oxide; however in some countries there is no upper limit. Typical use concentrations would be from 2% to 10% solids.
